The field of endoscopic surgery has become widely embraced by both surgeons and the public. The term "endoscopic" as used herein is defined to include the field of minimally invasive surgery including but not limited to endoscopic, laparoscopic, thoracoscopic and arthroscopic. There are numerous benefits associated with the use of endosurgical techniques including reduced trauma, reduced post-operative recuperation period, reduced incidence of infections, and reduced scarring. In addition, there tends to be a decrease in the length of endoscopic operative procedures when compared with conventional, open procedures, resulting in decreased time under general anesthesia. It is not unusual for patients who have undergone endoscopic surgical operations to be released from the hospital the next day after surgery and to be back on the job within several days. Recuperation periods of 2 to 4 weeks or more are associated with similar operations done using conventional, open surgical procedures.
Numerous endoscopic instruments have been developed which allow the surgeon to perform complex surgical procedures with minimal incisions into the skin and tissue surrounding a particular body cavity. In order to introduce the endoscopic instruments into a body cavity, it is first necessary to puncture and cannulate the body cavity by using a trocar. Trocars are widely known in the art and typically consist of an obturator and a trocar cannula. Trocars may have a protective housing or safety shield around the obturator which covers the sharp piercing tip of the obturator after insertion.
One type of trocar having an obturator safety shield is typically inserted by pressing the distal end of the trocar assembly against the outer skin of the patient with sufficient force to cause the piercing end of the obturator to pierce through the skin, underlying fat, muscle and fascia into a body cavity. Once the surgeon has properly positioned the trocar within the body cavity, the obturator and safety shield are removed, and, the trocar cannula is then available as a pathway, e.g., for the insertion of conventional endoscopic instruments and devices.
Conventional trocar obturators typically consist of an elongated obturator shaft having a distal piercing tip. The proximal end of the obturator shaft is typically mounted in an obturator handle. A biased safety shield for covering the piercing tip may be concentrically mounted about the obturator such that the shield is slidable between a fully extended position, wherein the piercing tip is covered, and a fully retracted position, wherein the piercing tip is exposed. The trocar obturator is, typically, concentrically mounted within a trocar cannula to form a trocar.
Conventional trocar cannulas typically consist of a distal cannula tube and a proximal cannula handle. The cannula tube is typically inserted into a patient (along with a section of the obturator shaft), while the proximal handle of the trocar cannula typically remains outside of the patient. Trocar cannula handles typically contain a spring-loaded flapper-type valve which seals the proximal opening of the trocar cannula, thereby allowing the patient's body cavity to remain insufflated with a gas by preventing the gas from escaping through the trocar cannula after the trocar obturator has been removed. The trocar cannula handle typically has an exterior control lever to manually control the position of the flapper valve and to indicate the position of the flapper valve.
Most surgeons prefer using a trocar having a protective sleeve or safety shield concentrically mounted about the trocar obturator. The safety shield is designed to help prevent the piercing tip of the trocar obturator from inadvertently piercing or cutting internal organs or blood vessels or tissue after penetration has been made through the layers tissue surrounding a body cavity. The safety shield typically operates in the following manner. When the distal end of the trocar is placed against the outer skin surrounding a patient's body cavity, the tip of the trocar obturator and the tip of the safety shield are typically in contact with the skin. As the surgeon pushes the trocar obturator into the layers of tissue and fascia surrounding the body, the concentrically mounted safety shield is displaced axially, against a biasing force, in a proximal direction to a retracted position, thereby exposing the piercing point of the obturator and allowing the tip to cut through tissue. The biasing force is typically provided by a spring member such as a compression spring. After the piercing tip has penetrated into the body cavity, the distal biasing force on the safety shield causes the safety shield to move rapidly in a distal direction to an extended position, thereby covering the piercing point of the obturator and preventing the obturator from piercing or cutting any internal tissue, organs, or blood vessels. Typically, the trocar assembly will have a locking mechanism which engages the safety shield and prevents the safety shield from displacing and uncovering the piercing tip of the obturator after the obturator has passed into the body cavity.
Although locking mechanisms for safety shields in trocar obturators are known in this art, there is a constant need in this art for advancement and progress with regard to the design of endoscopic surgical instruments, in particular with regard to the design of trocars and safety shield locking mechanisms for trocars.
Therefore, it is an object of this invention to provide a trocar having a safety shield and a lockout mechanism wherein the safety shield lockout mechanism is triggered by axial, proximal movement of the trocar obturator.
It is a further object of the present invention to have a locking mechanism for a safety shield of a trocar obturator which is reliable.